IAS17 Leases & IAS8 Accounting estimates

Hi

I wonder if anyone could help me.

If you spend 6m of leasehold improvements in year 2 of a 5 yr lease you would amortise the asset a 2m per year (6m/3 years).

However if one year later, yr 3, the company changes it’s decision making and signs a new 5 year lease. Now, do you

1) carry on amortising at 2m per yr for the remaining 2 years
2) amortise the amount in the balance sheet, ie 2m over 7 years (2yrs + 5yrs)
3) reinstate the prior period to amortising the original leasehold improvement value (6m) & amortise it over 10 years? (6m/10 years)

Thank you for your help.

Does anyone know where I can find evidence of this as back up